diff --git a/src/ProcessManager.php b/src/ProcessManager.php
index 1ff9f1ff..cd5e828c 100644
--- a/src/ProcessManager.php
+++ b/src/ProcessManager.php
@@ -32,6 +32,9 @@ class ProcessManager
 
     private static string $input = '';
 
+    /** @var ExecutableFinder|null Finder instance for mocking in tests */
+    private static ?ExecutableFinder $executableFinder = null;
+
     /** @var array Secrets to redact from error messages */
     private array $secrets = [];
 
@@ -81,14 +84,24 @@ public static function setBin(string $bin): void
         self::$bin = $bin;
     }
 
+    /**
+     * Set the ExecutableFinder instance for testing.
+     *
+     * @param ExecutableFinder|null $finder The finder instance or null to use default.
+     */
+    public static function setExecutableFinder(?ExecutableFinder $finder): void
+    {
+        self::$executableFinder = $finder;
+    }
+
     public static function guessBin(): string
     {
         if (isset(self::$bin) && self::$bin !== '') {
             return self::$bin;
         }
 
-        $finder = new ExecutableFinder();
-        $rclonePath = $finder->find('rclone', '/usr/bin/rclone', [
+        $finder = self::$executableFinder ?? new ExecutableFinder();
+        $rclonePath = $finder->find('rclone', null, [
             '/usr/local/bin',
             '/usr/bin',
             '/bin',
diff --git a/tests/Unit/ConfigurationTest.php b/tests/Unit/ConfigurationTest.php
index bcc7055f..6ae0387d 100644
--- a/tests/Unit/ConfigurationTest.php
+++ b/tests/Unit/ConfigurationTest.php
@@ -6,6 +6,7 @@
 
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Process\ExecutableFinder;
 use Verseles\Flyclone\CommandBuilder;
 use Verseles\Flyclone\ProcessManager;
 use Verseles\Flyclone\Providers\LocalProvider;
@@ -13,6 +14,21 @@
 
 class ConfigurationTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        // Mock ExecutableFinder to ensure tests run even without rclone installed
+        $mockFinder = $this->createMock(ExecutableFinder::class);
+        $mockFinder->method('find')->willReturn('/mock/path/to/rclone');
+        ProcessManager::setExecutableFinder($mockFinder);
+        ProcessManager::setBin(''); // Force re-guess
+    }
+
+    protected function tearDown(): void
+    {
+        ProcessManager::setExecutableFinder(null);
+        ProcessManager::setBin('');
+    }
+
     #[Test]
     public function set_and_get_timeout(): void
     {
diff --git a/tests/Unit/ProcessManagerTest.php b/tests/Unit/ProcessManagerTest.php
new file mode 100644
index 00000000..e6d65445
--- /dev/null
+++ b/tests/Unit/ProcessManagerTest.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Verseles\Flyclone\Test\Unit;
+
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+use Symfony\Component\Process\ExecutableFinder;
+use Verseles\Flyclone\ProcessManager;
+
+class ProcessManagerTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        ProcessManager::setExecutableFinder(null);
+        ProcessManager::setBin('');
+    }
+
+    #[Test]
+    public function guess_bin_returns_path_when_found(): void
+    {
+        $mockFinder = $this->createMock(ExecutableFinder::class);
+        $mockFinder->method('find')
+            ->willReturn('/usr/bin/rclone');
+
+        ProcessManager::setExecutableFinder($mockFinder);
+
+        $bin = ProcessManager::guessBin();
+
+        self::assertEquals('/usr/bin/rclone', $bin);
+    }
+
+    #[Test]
+    public function guess_bin_throws_exception_when_rclone_not_found(): void
+    {
+        $mockFinder = $this->createMock(ExecutableFinder::class);
+        $mockFinder->method('find')
+            ->willReturn(null);
+
+        ProcessManager::setExecutableFinder($mockFinder);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Rclone binary not found');
+
+        ProcessManager::guessBin();
+    }
+}